Gobipteryx
Gobipteryx is the name given to a genus of enantiornithine bird from the Late Cretaceous Period. Its fossils were found in the Barun Goyot Formation in the Gobi Desert, Mongolia and first described in 1974 from two fragmentary skulls (ZPAL-MgR-I/12 and ZPAL-MgR-I/32; Elżanowski, 1976). The type and only described species is Gobipteryx minuta.1 Elzanowski (1981) described seven specimens of G. minuta, found preserved still within their eggs. He documented evidence that the animals would have hatched with a superprecocial developmental pattern. 2 The genus also includes the fossil formerly known as Nanantius valifanovi, described from a fragmentary skull with some postcranial bones from Khermeen Tsav (PIN-4492). The synonymy was revealed through analysis of the first good specimen (IGM-100/1011), a supremely preserved partial skull from the Djadochta Formation at Ukhaa Tolgod.3 Gobipteryx was originally considered distinct enough to be classified in a distinct order (Gobipterygiformes) and family (Gobipterygidae). Research indicates it is a member of the Enantiornithes, a group of primitive birds which includes Neuquenornis and Sinornis. Description Based on a skull length of 45 millimeters, Gobipteryx has been estimated to be approximately the size of a partridge.3 Its bones are fibrolamellar. Skull The skull’s general shape is gradually tapering toward the front.1 Gobipteryx has a toothless beak1 formed from the fusion of the premaxillae bones.5 The skull is characterized as being rhynchokinetic1 with the pterygoid bones articulating with both the vomers36 and the palatine.13 The nares are tear shaped and the choana is located below them, more rosteral than in most modern birds.7 The nares are smaller than the antorbital fenestrae, a primitive feature for ornithurae birds.7 In addition, Gobipteryx's skull has an articulated rostrum.7 The jaw hinge is associated with the articulation of the quadrate with the pterygoid processes.1 The articular region of the mandible contains internal and retroarticular processes and has uniform symphysis.1 This animal has a large, uniform, and sutureless braincase. Vertebral column The vertebral column consists of at least 19 presacral vertebrae, the last 6 of these being dorsals.8 The neural spines of the twelfth and thirteenth vertebrae form the nuchal blade, which represents the point of greatest elevation in the vertebral column. shoulder girdle The scapula contains a prominent glenoid labrum and tapers backward, ending as thin rods.8 The coracoids are slightly concave anteriorly and are separate from the scapulae dorsally. They also stick out from the neck on either side.8 Gobipteryx's clavicles curve in a way that is consistent with that of other birds. Limbs The humerus is posteriorly convex (a normal trait for birds) and the head is comma-shaped.8 Gobipteryx's ulna is about twice as thick as the radius.8 Metacarpals II and III have been found in embryonic fossils and are observed to be about equal size and are in close contact with each other. Paleobiology Flight Gobipteryx is believed to have been capable of flight.48 The scapula is long, and therefore, well suited for flight by having more area for muscle attachment.8 In addition, the forelimb of Gobipteryx is more than twice the length of the thorax, falling within the acceptable range observed in flying birds. Development Gobipteryx, along with other enantiornithes, is thought to have superprecocial development, in which it was capable of flying upon hatching.48 Evidence for this comes from the fact that the forelimbs and shoulders of advanced embryos are almost completely ossified.8 In addition, the growth of G. minuta has been shown to slow down immediately following hatching.4 This suggests that it was highly mobile in its life, since locomotion has been shown to slow the growth of young birds by focusing energy and resources elsewhere.4 This onset of flight so early in life is not seen in most modern birds, which begin flying when they have reached or are close to full size. History Category:Cretaceous birds Category:Prehistoric birds of Asia Category:Gobipterygiformes